Narrative:

On inbound flight, both main fuel tanks had been fueled to capacity, 9500 pounds each, and center tank to 5000 pounds. We burned center fuel per procedure until tank was dry, which took us into descent. A short time later I noticed an imbalance between tanks 1 and 2 of 600 or 700 pounds (limit imbalance is 1000 pounds). Although this is not too unusual to see and the gauges on this model aircraft see-saw up and down several hundred pounds, I opened the cross-feed and turned off the pumps in the low #1 tank, to try to even out the fuel somewhat. However we were descending and slowing and the throttles were at idle; making fuel flow low and balancing tanks a slow procedure. Thus after several minutes it did not seem unusual to see little or no movement on the fuel quantity gauges. By then, we were into a busy approach with autoplt on MEL and I 'cleaned up' the fuel panel for approach and landing. On post flight, total fuel was about 8400 pounds in #1 and 9100 in tank #2 which seemed pretty close to what was expected. On departure dispatch fuel was 18100 pounds and we read 9100 on each tank after fueling and we departed after a very quick turn around. Very soon after takeoff, we noted that #2 tank was not decreasing as it should with climb fuel flow and we realized we had a gauge stuck at 9100 pounds. After trouble shooting, cycling circuit breaker's etc, and calculating fuel usage and total fuel added, we were pretty sure we were about 1500 pounds short in tank 2. However, since we had made a couple of assumptions in those calculations, we could not be absolutely sure of how much fuel was aboard and we decided to divert to an airport short of destination with good WX and where we had adequate fuel even from our good gauge alone. Our company recently decided to do away with fuel slips from fuelers, however our departure station apparently had not gotten that word yet fortunately since we would not have been able to do the calculations which turned out to be right on the mark without it. Also from now on, I will test my gauges after each refueling and airborne before balancing tanks not just on receiving aircraft check.

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Original NASA ASRS Text

Title: MLG DIVERTS TO AN ALTERNATE AND LANDS WHEN IT BECOMES QUESTIONABLE IF THE FUEL REMAINING IS ENOUGH TO FLY TO DEST.

Narrative: ON INBND FLT, BOTH MAIN FUEL TANKS HAD BEEN FUELED TO CAPACITY, 9500 LBS EACH, AND CENTER TANK TO 5000 LBS. WE BURNED CENTER FUEL PER PROC UNTIL TANK WAS DRY, WHICH TOOK US INTO DSCNT. A SHORT TIME LATER I NOTICED AN IMBALANCE BTWN TANKS 1 AND 2 OF 600 OR 700 LBS (LIMIT IMBALANCE IS 1000 LBS). ALTHOUGH THIS IS NOT TOO UNUSUAL TO SEE AND THE GAUGES ON THIS MODEL ACFT SEE-SAW UP AND DOWN SEVERAL HUNDRED LBS, I OPENED THE CROSS-FEED AND TURNED OFF THE PUMPS IN THE LOW #1 TANK, TO TRY TO EVEN OUT THE FUEL SOMEWHAT. HOWEVER WE WERE DSNDING AND SLOWING AND THE THROTTLES WERE AT IDLE; MAKING FUEL FLOW LOW AND BALANCING TANKS A SLOW PROC. THUS AFTER SEVERAL MINUTES IT DID NOT SEEM UNUSUAL TO SEE LITTLE OR NO MOVEMENT ON THE FUEL QUANTITY GAUGES. BY THEN, WE WERE INTO A BUSY APCH WITH AUTOPLT ON MEL AND I 'CLEANED UP' THE FUEL PANEL FOR APCH AND LNDG. ON POST FLT, TOTAL FUEL WAS ABOUT 8400 LBS IN #1 AND 9100 IN TANK #2 WHICH SEEMED PRETTY CLOSE TO WHAT WAS EXPECTED. ON DEP DISPATCH FUEL WAS 18100 LBS AND WE READ 9100 ON EACH TANK AFTER FUELING AND WE DEPARTED AFTER A VERY QUICK TURN AROUND. VERY SOON AFTER TKOF, WE NOTED THAT #2 TANK WAS NOT DECREASING AS IT SHOULD WITH CLB FUEL FLOW AND WE REALIZED WE HAD A GAUGE STUCK AT 9100 LBS. AFTER TROUBLE SHOOTING, CYCLING CB'S ETC, AND CALCULATING FUEL USAGE AND TOTAL FUEL ADDED, WE WERE PRETTY SURE WE WERE ABOUT 1500 LBS SHORT IN TANK 2. HOWEVER, SINCE WE HAD MADE A COUPLE OF ASSUMPTIONS IN THOSE CALCULATIONS, WE COULD NOT BE ABSOLUTELY SURE OF HOW MUCH FUEL WAS ABOARD AND WE DECIDED TO DIVERT TO AN ARPT SHORT OF DEST WITH GOOD WX AND WHERE WE HAD ADEQUATE FUEL EVEN FROM OUR GOOD GAUGE ALONE. OUR COMPANY RECENTLY DECIDED TO DO AWAY WITH FUEL SLIPS FROM FUELERS, HOWEVER OUR DEP STATION APPARENTLY HAD NOT GOTTEN THAT WORD YET FORTUNATELY SINCE WE WOULD NOT HAVE BEEN ABLE TO DO THE CALCULATIONS WHICH TURNED OUT TO BE RIGHT ON THE MARK WITHOUT IT. ALSO FROM NOW ON, I WILL TEST MY GAUGES AFTER EACH REFUELING AND AIRBORNE BEFORE BALANCING TANKS NOT JUST ON RECEIVING ACFT CHK.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.